1. Field of the Invention
The invention relates to a portable power wrench comprising a housing with a rotation motor, a gear casing including a gearing and an output shaft, wherein the gear casing is rotatively and/or releasably connected to the housing via a swivel or multi-position connection.
In particular the invention concerns a power wrench of the above type wherein at least one operation parameter sensing device is located in the gear casing and connected to an operation control unit, and a means for transferring signals between the operation parameter sensing means in the gear casing and the housing.
2. Description of the Related Art
In power wrenches provided with operation parameter sensing devices like torque transducers it is an advantage from the signal accuracy point of view to locate the torque transducer as close as possible to the screw joint being tightened, e.g. on the output shaft of the power wrench or at least on a rotating part in the gear casing. This is a previously well known want. It is also previously known to have sensing means activating power as well as generated signals transferred between the sensing means and the wrench housing via different types of signal transferring means.
A particular signal transmission problem occurs in power wrenches having a forward gear casing that is rotatively and/or releasably supported on the power wrench housing via a swivel or multi-position connection. A power wrench of this type is previously described in for instance U.S. Pat. No. 4,485,698. When such a power wrench is provided with one or more operation parameter sensing devices located in the gear casing the signals generated thereby have to be transferred from the gear casing to an electronic operation control unit which is provided either in the tool housing or in a stationary unit separate from the power wrench. In both cases there is a requirement to obtain a simple yet reliable transfer of signals from the sensing device or devices in the gear casing to a wiring in the housing for further transport to a control unit, in the housing or at a remote location.